To investigate the role of the hippocampal formation (HF) in feeding behavior, single neuron activity in the monkey HF was recorded during performance of an operant task that included food/nonfood discrimination, drinking, and active avoidance. Of 837 neurons recorded in the HF, 155 responded to the sight of one or more objects. Of these, 82 responded to the sight of different objects with different response magnitudes, and some of these 82 responded predominantly to food-related (rewarding) objects or nonfood, aversive objects. The magnitude of response of neurons that responded predominantly to food was not necessarily correlated with the order of animal's preference for those kinds of food. For some neurons that responded predominantly to food or nonfood, effects of extinction or reversal learning on the neuronal responses were tested, and most of the neurons tested maintained their original responsiveness even after behavioral extinction or reversal learning was accomplished. The results suggest that these HF neurons may be involved in preservation of past information concerning food or nonfood.